Understanding asthma-chronic obstructive pulmonary disease overlap syndrome

Abstract

Asthma-chronic obstructive pulmonary disease overlap syndrome (ACOS) is a loosely-defined clinical entity referring to patients who exhibit characteristics of both asthma and chronic obstructive pulmonary disease (COPD). Clinical definitions and classifications for ACOS vary widely, which impacts our understanding of prevalence, diagnosis and treatment of the condition. This literature review was therefore conducted to characterize the prevalence of ACOS and the effect of different disease definitions on these estimates, as this has not previously been explored. From an analysis of English language literature published from 2000 to 2014, the estimated prevalence of ACOS ranges from 12.1% to 55.2% among patients with COPD and 13.3%-61.0% among patients with asthma alone. This variability is linked to differences in COPD and asthma diagnostic criteria, disease ascertainment methods (spirometry-based versus clinical or symptom-based diagnoses and claims data), and population characteristics including age, gender and smoking. Understanding the reasons for differences in prevalence estimates of ACOS across the literature may help guide decision making on the most appropriate criteria for defining ACOS and aid investigators in designing future ACOS clinical studies aimed at effective treatment.

Asthma–COPD overlap syndrome (ACOS) in primary care of four Latin America countries: the PUMA study

“…The findings of the present study are consistent with those reported in some general and selected COPD populations that have used the previous diagnosis of asthma plus spirometric COPD to define ACOS [3, 5, 7, 30]. The comparison with the PLATINO study deserves special consideration as this is another study from Latin America that use the same two ACOS definitions in the same population [3].…”

“…The prevalence of ACOS in the total population ranges from 1.6 to 4.5% in different studies around the world [1–5]. If only subjects with asthma or COPD are included, the prevalence of ACOS among patients with COPD ranges from 12.1 to 55.2%, and among patients with asthma from 13.3 to 61.0% [1–19].…”

What is asthma−COPD overlap syndrome? Towards a consensus definition from a round table discussion

“…Without such a case definition, it is impossible to collect (let alone interpret) data on its epidemiology, clinical course or therapeutic responsiveness. This lack of consensus, for instance, may explain the widely divergent data on the prevalence of ACOS, which ranges between 11% to 56% among patients previously diagnosed with COPD [35], 13% to 61% among patients previously diagnosed with asthma [76] and ∼2% in the general population over 40 years of age [77]. It may also explain why in some studies, ACOS has been associated with more female patients [78,79], while in others with more male patients [30,80].…”

Prevalence and characteristics of asthma–COPD overlap syndrome identified by a stepwise approach

“…The proportions of ACOS patients among COPD patients in real-life clinical settings have been estimated in several reports previously 3. However, the designs and sampling methods of these studies have varied, and the prevalence values have ranged from 12% to 55%, mainly because of the difference between the definitions of ACOS followed in each study, including airflow reversibility, spirometry, and clinical diagnosis 3.…”

“…However, the designs and sampling methods of these studies have varied, and the prevalence values have ranged from 12% to 55%, mainly because of the difference between the definitions of ACOS followed in each study, including airflow reversibility, spirometry, and clinical diagnosis 3. Such discrepancies in the definition of ACOS have complicated our understanding of the epidemiology and clinical characteristics of this disease in terms of the symptoms, frequency and severity of exacerbations, and disease burden.…”